Method of cold flattening blocks



y 9, 1956 G. SCHAMING 2,747,267

METHOD OF COLD FLATTENING BLOCKS Filed Jan. 7, 1953 F/& 5 ll i I! 6 I 1 i F/G. 6 9 l0 GU/Y/aUme ZZZ 'Eg [xi M 4 A ffomeys United States Patent METHOD OF COLD FLATTENING BLOCKS Guillaume Schaming, Richmond (Surrey), England, assignor to Societe Schostal, Vaduz, Liechtenstein, a jointstock company Application January 7, 1953, Serial No. 330,104

Claims priority, application Switzerland January 15, 1352 4 Claims. (Cl. 29--417) The present invention relates to the cold stamping of any material lending itself to such type of work, metallic or otherwise. Blocks of uniform weight, equal to that of the part to be made, are started with. Such blocks may advantageously be obtained by shearing bars. However, the ratio of the length of the bars to their diameter cannot be below a certain limit.

If, in the part to be made, this ratio is lower, one is led to cut longer blocks out of a bar of smaller cross section, then flatten said blocks in a die, along their axes, in a step preliminary to the shaping step. However, during this flattening step, the blocks tend to crack or split along their edges, which makes them unsuitable for subsequent work.

The invention has for its objects to avert this drawback. It is characterized in that the flattening step is performed under such conditions that at least one of the faces of the flatened block is made slightly convex.

A curved shape, for instance an exceedingly slight sphericity or a conical shape, may be imparted to one or both faces of the flattened block. It is generally sufficient that the edge of the convex face or faces make an angle of about 1 with the cross sectional plane of the block.

The accompanying drawing represents, by way of example, some embodiments of the invention.

Fig. 1 shows in side elevation, a block which is to be flattened along its axis;

Fig. 2 is the corresponding plan view;

Figs. 3 and 4 illustrate, respectively in elevation and in plan, the same block flattened according to the invention;

Fig. 5 is an axial sectional view of a tool usable in this instance;

Fig. 6 is a modification of Fig. 3;

Figs. 7 and 8 show other modifications of Fig. 3, Fig. 7 being an elevation and Fig. 8 an axial section.

In the selected example, the initial block 1 (Figs. 1 and 2) is obtained by sectioning a cylindrical bar. The ratio between its length and its cross section is substantially at the lower limit attainable by shearing. The part to be made is considerably flatter and larger in diameter. One therefore has to flatten out the block 1, along its axis, to impart the desired proportions to it (Figs. 3 and 4). To avoid the occurrence of cracks on the edge of the block during its flattening step, the latter is eifected under such conditions that the flattened block 2 has both its faces 2a2b convex.

For this purpose, one may use, as shown in Fig. 5, a die 3 whose punch 5 and extractor 6 have concave end faces. Preferably one associates with the dies a device for centering the blank in the die prior to flattening.

It may be enough that only one of the faces of the 2,747,267 Patented May 29, 1956 flattened block has a convex form as shown at 2a in Fig. 6.

In the case where the production under consideration relates to washers or rings, it is possible to obtain two washers from a single block. The initial block is flattened, as in the case of Fig. l, but so as to leave in its central portion a thickness which corresponds to the weight which the second washer is to have. This central portion is then removed by the action of a punch 8 (Fig. 7), and there is obtained on the one hand a blank 9 for the first ring, and on the other hand a piece of scrap 10, 10' which subsequently is flattened again for the production of the second washer. Should the need arise, the scrap may be used for the production of a disk rather than a washer (Figs. 7 and 8).

The following example is given by way of illustration. It is desired to produce at a high rate, without loss of metal, sound washers of mild steel, having a diameter of 44 mm. and a thickness of about 6 mm., Weighing grams.

If the blanks for such washers Were sawed off from a bar, the loss of metal would be from 35 to 40%, and the operation would be long and costly. Moreover, one cannot obtain blanks of such small thickness by shearing. Accordingly, parts weighing 70 grams are sectioned by shearing bars 25 mm. in diameter. The sections obtained then have a thickness of about 18.4 mm. Or blanks are made from a bar 30 mm. in diameter, and the sections in this case are about 12.7 mm. in thickness. The saidvsections are then flattened, until their diameter attains 44 mm. If sections 25 mm. in diameter were started with, the increase in diameter would be It would be 146% if sections 30 mm. in diameter were started with.

By imparting, according to the invention, a convexity to one at least of the faces of the flattened section, the convexity being such that the edge of the convex face or faces will make an angle of about 1 with the cross sectional plane of the flattened blank, the latter will not show any cracks around its periphery.

What I claim is:

1. The method of cold-forming a cylindrical block out from bar stock to decrease its thickness and increase its diameter within the confines of a circular die without producing edge cracks in the resulting blank comprising the steps of subjecting the block to axial pressure to cause it to flow radially outwardly toward the wall of said die, and causing the thus outwardly flowing material of the block to fiow between outwardly radially converging surfaces whereby the resulting blank has a slight spherical convexity on at least one of its faces.

2. The method of claim 1 wherein said convexity is of such degree that the edge of a convex surface makes an angle of about 1 with the cross sectional plane of the said blank.

3. The method of claim 1 wherein the said blank is formed with a slight convexity on both of its surfaces.

4. The method of claim 3 wherein the convexity of the surfaces of the blank is of such degree that the edges of the convex surfaces each make an angle of about 1 with the cross sectional plane of said blank.

References Cited in the file of this patent UNITED STATES PATENTS 1,082,910 Rockwell Dec. 30, 1913 2,360,354 Lyon Oct. 17, 1944 2,644,352 Ressegger July 7, 1953 

